Electrostatic controls and memory systems



J. w. DIESEL 2,931,954

ELECTROSTATIC CONTROLS AND MEMGRY SYSTEMS 2 Sheets-Sheet 1 April 5, 1960 Filed March 14, 1956 FIG. 3

63 6.6' 69 A\{{\'\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\iw l lli JOHN W D/ESEL,

April 5; 1960 J. w. DIESEL 2,931,954

ELECTROSTATIC CONTROLS AND MEMORY SYSTEMS Filed March 14, 1956 2 Sheets-Sheet 2 JOHN w D/ESEL,

United States Patent() ELECTROSTATIC CONTROLS AND MEMORY SYSTEMS John W. Diesel, Maplewood, Mo., assignor to Erdco, Inc., Maplewood, M0., a corporation of Missouri Application March 14, 1956, Serial No. 571,487

14 Claims. (Cl. 317-144) 'This invention relates to electrostatic controls, and more particularly to permanent-storage electrostatic control devices and to memory systems, such as might be used for computers, business machines and the like.

In my copending applications, Serial No. 441,057, filed July 2, 1954 (of which this is a continuation-in-part) and Serial No. 571,098, filed March l2, 1956, now Patent No. 2,885,509, for Electrostatic Relays, I have disclosed certain electrostatic relays which may be used in computers and 'business machines. Briefly, the relays have at least one fixed plate and a movable plate, which movable plate is normally biased away from the fixed plate to an off position. The iixed plate is connected to ground or the negative side of a D.C. power supply. When the movable plate is then connected through an excitation input circuit to the positive side of the power supply, the movable plate is charged and drawn toward the fixed plate. Contacts are actuated by the movable plate, and a release resistor provides for discharge of the movable plate when the input circuit is opened. In the above patent applications, the movable plate is constituted by a hinged flap or relay arm with a movable contact on the free end cooperating with one or more fixed contacts. The bias for opening the contacts may be from the springiness of the relay arm, or the bias may be electric in the sense that a second plate is mounted over the movable plate and permanently connected to the positive side of the power supply.

A storage action is achieved by providing a hold circuit for the .movable plate. The hold circuit includes a normally-closed clear switch and a contact which is in conductive cooperation with the movable plate when the latter is in its "on position. In other words, the hold circuit provides a second path for exciting the movable plate. The excitation input circuit may then be opened, and the relay will remain in its on or actuated position. Return to the off condition is effected by opening the clear switch. When such relays are provided with a hold circuit, they may act as temporary storage devices, but they have the disadvantage of automatically returning to their off condition if the power is interrupted. The present invention contemplates a permanent storage device which will remain in its on condition although all power is removed.

Briefly, this permanent storage device has upper and lower fixed plates of high resistance, the upper one of which is permanently connected to the positive side of the power supply and the other one of which is connected to the negative side of the power supply. The relay arm is then formed as a strip extending between the plates with low-resistance conductive areas on its top and bottom surfaces cooperable with the upper and lower fixed plates. Both ends of this strip are secured in such fixed spaced relationship to the fixed plates as to introduce a buckle in the center portion and the buckle has an overcentering effect tending to maintain the relay arm in its on or olf position, whichever is the case prior to loss of power.

Patented Apr. 5, 1960 A release resistor is connected from the movable plate to ground, and the input excitation circuit is adapted to connect the movable plate to the positive terminal of the power supply. When the excitation circuit is open, the movable plate assumes a negative potential and is drawn up against the positive fixed plate. If the input circuit is closed, then the movable plate is charged positive and is drawn toward the negative lixed plate to its on position. In its on position, the movable plate connects with a fixed contact which is connected through a normally-closed clear switch to the positive side of the power supply so that the movable plate continues to be positive even though the input circuit is opened. The relay is returned to its off position by opening the clear switch.

The invention further contemplates a memory system in which such relays may be used to advantage. Heretofore, memory systems have had a high initial cost which precludes their use in low-cost machines. Much of the cost can be attributed to the coding apparatus for converting numbers into electric signals. For example, in electronic machines, a number is usually represented by a predetermined pattern of pulses fed in sequence. Although such pulses can be handled rapidly and conveniently by electronic tubes and magnetic memory systems, the apparatus is very expensive. Accordingly, one of the objects of this invention is to provide a relatively inexpensive memory system for business machines. An-

other object is to provide a memory system particularly suited for use with electrostatic computers and business machines, which have cost advantages over more conventional electronic machines. It should be understood, however, that the memory system is also adaptable for other types of computers, such as conventional mechanicalY (gear-type) calculators or perhaps electronic machines. At present, calculators are not capable of handling more than a few accounts, hence it is necessary to transfer from and to ledgers, a procedure that is tedious and conducive to errors. This invention contemplates an arrangement that will permit a large number of accounts to be maintained in the machine.

Briefiy, numbers or other items of information are fed into storage in the form of a pattern of energized and non-energized conductors. A conductor is energized when it is connected to the positive terminal of the power supply so as to have an electric potential with respect to ground or a common return. For example, a one-digit number could be represented by ten conductors corresponding to numerals zero through nine Numeral two is then indicated by energizing the numeral two conductor, the other nine conductors being deenergized or at "ground potential. A second digit could be represented by a second group of conductors, etc. Numbers are stored in the form of a pattern of on or off relays. For example, a single digit number could be represented by ten relays corresponding to numerals zero through nine The number two is fed to storage by exciting the input or excitation conductor for the numeral two relay, which relay is then actuated to its on condition. It the relay remains in its on condition after the excitation input conductor is deenergized or disconnected from the positive terminal of the power supply, then the number two is in storage. This number is read out of storage by a multiple-conductor bus connected to be energized from the actuated or on relay.

In other words, each digit of a number is represented by a group of conductors or relays, which may be referred to as a digit group. Several digit groups may be provided in order to handle multiple-digit numbers. The several digit groups of conductors, which together represent a complete number, `constitute a bus. Usually, .only

one conductor in each digit group is energized at any given time, but a code system might be employed so that fewer conductors are required in each digit group. Also, a single digit group of conductors might be made to serve several different digits, as by use of a synchronized switching system or by separate isolated return circuits. In other words, the same group of conductors might be employed to serve a tirst digit group at time A or by return circuit A; the second digit at time B or by a return circuit B, etc.

rl'he invention additionally contemplates that the storage relays will be arranged in banks, each bank being adapted to store a different number. Any given bank of storage relays is connected to the bus by an associated multiple-pole address relay, so as to receive or read out a number. Also, any selected bank of relays may be cleared without clearing the other banks.

Other features of the invention will be in part apparent from and in part pointed out in the following detail description taken in connection with the accompanying drawings, in which:

Fig. l is a circuit diagram showing how a plurality of storage relays may be arranged in groups and in banks so as to be selectively connected to a transfer bus and selectively cleared;

Fig. 2 is a diagram illustrating the circuit connections of a permanent storage device, embodying the invention;

Fig. 3 is a transverse cross section illustrating how the plastic panels are stacked to form a bank of storage relays;

Fig. 4 is a top plan view of the base panel;

Fig. 5 is a top plan view of an overlying spacer frame;

Fig. 6 is a top plan view of the relay-arm panel, which overlies the lower spacer frame;

Fig. 7 is a bottom plan view of the relay-arm panel;

Fig. 8 is a top plan view of upper spacer frame; and

Fig. 9 is a bottom plan view of a top panel.

The memory system diagrammatically shown in Fig. 1 includes a series of permanent-storage devices generally designated SA, which may be electrostatic relays operating the devices under the principles disclosed in the aforementioned copending patent applications. As shown in Fig. 2, there is a high-resistance conductive surface or upper plate P1 and a high-resistance conductive surface or lower plate P2 fixed in spacer relation so as to accommodate a movable plate MP of low-resistance conductive material. The upper fixed plate is permanently connected to the positive side of a high-voltage power supply, whereas the two portions of the lower fixed plate are connected to the negative side of the power supply through ground.

As explained in the prior patent applications, the voltage supply is of high voltage, for example two thousand volts, and the resistance values of the fixed plates are rather high, so as to limit the current drawn to very low values. The movable plate is also connected through a release resistor R to the negative side of the voltage supply through ground, and the resistance R is of very high value. For example, the current drawn by the release resistor and plates may be less than twenty-five microamps.

The movable plate is also adapted to be connected through an input excitation circuit IC and switch SI to the positive side of the power supply. An output circuit OC including switch SO might also be provided to lead from the movable plate. A fixed Contact FC is located at a gap in the lower plate and is connected through a hold circuit HC to the positive side of the power supply. The hold circuit includes a normally-closed clear switch CS, and the fixed contact FC cooperates with a movable Contact MC on the movable plate.

Since the movable plate is permanently connected by the release resistor R to ground, it initially has a lower potential than the upper tixed plate P1 and the movable plateis drawn toward or against the upper plate. When the input switch SI is closed, the movable plate receives a positive charge equal to that of the upper xed plate P1, and the movable plate in then attracted toward the lower plate P2. In its on or actuated position, the movable plate or contact MC engages the fixed contact FC so as to receive a positive charge from the hold circuit also. The input switch Si may then be opened without causing the movable plate to return to its oi position.

When it is desirable to read out of storage, the switch SO is closed and a positive signal passes through the hold circuit and movable plate MP out the output circuit OC. The relay is cleared or returned to its off position by opening the clear switch CS, in which event, the positive charge on the movable plate MP is drained by the release resistor R so that movable plate becomes relatively negative and moves upwardly to its ofi position.

` Referring now to Figsj3-9, a series of such storage relays may be conveniently made from stacked panels of insulating material in a manner similar to that described in the aforementioned copending patent applications. As will be more apparent, it is desirable to have a number of such relays, in order to represent a multiple-digit number. For example, there might be eighty relays representing an eight-digit number, the rst ten relays corresponding to numerals zero through nine for the first digit, a second ten relays corresponding to numerals zero through nine for the second digit, etc. The relays for one number can be arranged in a row or bank, and since the devices are reasonably compact, the cost is not excessive. A bank for one account or point of storage may then be stacked upon a bank for a second account, etc. Each bank will include a multiple-pole address relay and also a normally-closed hold relay, as will be more apparent hereinafter.

A bank of storage relays comprises a base panel 1, a spacer frame 3, a relay-arm panel 5, a second overlying spacer frame 7 and a top panel 9. These panels are formed from plastic sheets and films, such as laminated phenolic, vinyl or polyesters. The base panel is relatively rigid, and its top surface is provided with two spaced conductive areas 11 of high-resistance material, such as carbon paint. As such, the conductive areas 11 define the lower xed plate and connect with low-resistance leads 13 along their outer front and back margins, which leads 13 are connected together at 14 and to an input terminal 15 at one end of the panel. An elongate narrow contact 17 extends in insulated relationship across the panel 1 between the two portions 11 of the negative plate to act as a fixed contact FC for the several relays. This strip 17 might be formed as a strip of contact metal, such as stainless steel, adhered or laminated to the base panel. The contact 17 connects with terminal 19 at the end of the panel.

Spacer frame 3 overlies the base panel to form upward projections at the ends or margins thereof and the spacer frame might be one-sixteenth to one-thirty-second of an inch thick, the center portion of the frame being cut away to expose the conductive areas 11 and 17. The crossover holes at 21 and 23 are formed at one end of the spacer frame for registered cooperation with the conductive terminal portions 15 and 19, respectively. It will be understood that the cross-over holes are at least in part filled with low-resistance conductive material, such as silver paint, so as to complete a circuit through the spacer.

The relay-arm panel overlies the lower spacer frame 3, and this panel preferably is of relatively thin insulating material, such as the Du Pont tilm Mylar one-thousandth of an inch thick. The strip is slotted at 25 to provide a plurality of intervening narrow strips extending between the front and back margins of the panel, each strip corresponding to a relay arm for a different relay. The top and bottom surfaces of each strip are coated with low-resistance conductive material, such as silver paint',

vacuum deposited metal vapor (i.e., Metallized Mylar) or metal foil, in order to provide low-resistance conductive areas 27, which form the conductive movable plate. This panel is also somewhat wider than the other panels and its ends are cut at 29 so as to permit the front and back margins 31 and 33 of the panel to be pushed inwardly, so that the length of the strips is greater than the straight-line distance between the secured ends, thereby to introduce a buckle in the several relay arms or movable plates 27. The extent of this buckle is sufcient to provide an overcentering orV snap-action effect. Movable contact elements 34 are mounted on the lower portion of the relay arms 27 in conductive relation for cooperation with fixed contact 17. The panel 5 also has a lead-carrying portion 35 projecting from the front margin 31, which lead-carrying portion 3S facilitates connection with other apparatus such as the secondary circuits for a corresponding address relay.

Leads 37 extend across one or both faces of the panel to the movable plate areas 27, the movable plate areas for each relay arm being connected together by crossover holes 39. The release resistors may also be formed on the panel as lines 41 of high-resistance conductive material, such as carbon paint. The release resistors 41 might be disposed along the back margin of the relayarm panel and the several resistors 41 connect with common `low-resistance leads 43. The lead 43 connects with aterminal lead 45 at one end of the panel. The terminal lead 45 includes a cross-over hole 47 adapted to register with conductive portion 21 of the underlying spacer 3. Another terminal lead 49 and cross-over hole 51 register with the conductive terminal 23 in the spacer. Leads 45 and 49 extend across a projecting portion 53 of the panel, which portion 53 is connected to the power supply and hold circuit. Accordingly, a circuit is established by leads 45 and 49 to the lower plate 11 and fixed contact 17, respectively.

A third terminal 55 cooperates with a cross-over hole V59 .in the upper spacer frame 7. This cross-over hole is filled with conductive material so as to register with a terminal 62 on the upper panel 9. The upper panel 9 has an area 60 of high-resistance conductive material forming the upper fixed plate which plate is connected to the terminal 62 by low-resistance leads 58 extending along the front and back margins.

The several panels are stacked as indicated in Fig. 3 toform a unit. To facilitate such assembly, each panel may 4have corner holes 61, through which rods 63 are inserted. The panels are then pressed together, as by nuts 65 `threaded over the rods. In practice, each unit would store a multiple-digit number, and a series of units would be stacked together on a base 67, a cap 69 being Provided to hold all panels in pressure engagement.

t will be understood that the relay arms or strips are exible and have a limited degree of resilience, so that an overcentering effect is achieved by the buckled configuration. This mechanical bias should be sucient to hold the relay arm in either its on or its olif position, whichever is the case prior to removal of all power. On the other hand, the mechanical bias should be less than the electrostatic forces developed in normal operation.

Referring now back to Fig. l of the drawings, it should be understood that numbers or other items of informa- .tion are represented by a pattern of energized and nonenergized conductors in a transfer bus. For example, the bus may include a first digit-group of ten conductors corresponding tov the numerals zero through nine" of a first digit of a number, a second digit group of ten conductors corresponding to numerals zero through "nine of the second digit, etc. With this arrangement, a transfer bus for an eight-digit number would have eighty conductors or eight digit-group conductors. Only one conductor in a digit group s energized at any given time. Accordingly, the number thirty-four would be n- .ftiicated when the numeral three conductor of the second digit group .and the numeral four conductor of the rst digit group are energized, the other conductors being non-energized. A conductor is energized when it is connected to oneterminal of a power supply, the other terminal being connected to ground. For purposes of clarity, only tive .conductors of the bus B are shown in Fig. l, but .it should be understood that there could be a much larger number.

A number fed into the memory system by the transfer bus can be stored in a selected account or point of storage, only two such accounts .being shown in Fig. l, although there would normally be many more. Each account includes a normally-open multiple-pole address relay, a bank of storage relays, and a normally-closed clear relay. In Fig. l, there are two accounts A and B, hence two address relays AA and AB. The address relay AA is associatedv with a bank of storage relays SA and a clear relayCA; whereas the address relay AB is associated 1with .a .bank of storagerelays SB and a clear relay CB.

Each bank of storage rrelays includes a separate relay for each conductor of they transfer bus B, and each relay is .connected to one of the bus conductors through a separate set of contacts or pole of the associated address relay. For example, the transfer bus may have conductors B1 through BS, which are connected respectively to vpoles AAI through AAS of the address relay AA. The poles AAI through AAS are then connected respectively to storage relays SA1 through SAS. Similarly, the address relay AB has poles ABl through ABS connected to bus conductors El .through B5 and to storage relays SBI through SBS, The connections to the storage relays correspond to the movable plate or relay arm leads 37 previously described.

The hold circuit leads 49 for all storage relays (SA and SB) .are connected to a common hold circuit HC. This circuit leads through a normally-closed clear switch CS to the `positive terminal of the power supply. In order to permit selective clearing of the accounts the hold circuit leads 49 of each bank are also connected to the positive terminal of the supply through a second hold or clear circuit CC having clear relays for each account. A normally-closed ciear relay CA is associated with the storage devices SA, whereas a clear relay CB is associated with storage devices SB. The excitation .input EA to relays AA and CA is then connected through an address switch RA to the supply, the excita tion input EB for relays AB and CB being energized through another address switch RB.

Operation is as follows: One of the conductors .for each digit group in the transfer bus B is energized to represent a given number, which is to be stored. For purposes of explanation, assume conductor B1 is energized. If this number is to be stored in account A, the associated address switch RA is closed to actuate address relay AA and close contacts AAI through AAS. The storage relays for account .A are thus connected to the bus, and in this example, .storage relay SA1 is actuated to its on" condition by bus conductor B1. The relay arm moves to its down position and engages the fixed contact of the hold circuit. Thereupon, a circuit is completed through the clear-switch CS and hold circuit HC to the movable plate. The bus conductor B1 may now be deenergized and the storage relay SAI will remain in its on or actuated condition, even when address relay AA is opened.

The actuated relay will even remain in the on condition if all power is removed, the buckle overcentering effect tending to maintain the relay arm in proper position. At some later time, the number is read out of storage account A by again closing the address switch RA. A circuit is then completed through the switch CS, hold circuit HC and closed or on relay SA1 to the bus conductor B1 through AAI. The bus conductor Y 7 B1 is thereby energized from the memory so that it can control other apparatus.

In other words, a keyboard or the output of an addition system energizes certain bus conductors, the particular energized conductors representing a particular number. This number is stored by connecting all bus conductors to one bank of storage relays, so that particular relays are actuated to an on condition. Address switch RA is opened and another number represented by a new pattern of energized bus conductors may then be stored in account B by closing and opening address switch RB. Subsequently, the same ous may be used to transfer either stored number back to the arithmetic system or to an answer register by closing the proper address switch RA or RB. The numbers remain stored until the clear switch CS is opened.

Normally, it is not desirable to clear all of the accounts, hence the address switches also permit selection of the account to be cleared. For example, if RA is closed, clear relay CA is actuated to open its contacts. When the clear switch CS is then opened, both of the hold circuits HC and CC for storage relays SA are interrupted and all on storage relays SA return to their olf condition. On the other hand, the hold circuit CC for account B remains closed at clear relay CB (which is not actuated) so that the on storage relays SB are not eected by opening of the clear switch CS.

From the foregoing description, it will be apparent that the storage devices and memory system herein disclosed are especially adapted for computers of the type having electrostatic relays, although the apparatus is also applicable to other types of computers. Moreover, the apparatus is relatively inexpensive since the circuits and relays can be readily manufactured by printed circuit techniques. Although other types of address relays could be used, the invention particularly contemplates the use of multiple-pole electrostatic relays for the address relays and clear relays, as well as for storage relays.

Whereas the specific disclosure contemplates an arrangement wherein there will be a separate digit group of ten bus conductors and associated relays for each digit of a number, other arrangements might be utilized. For example, the quantity of storage relays and bus conductors may be reduced appreciably by using a coding system. A one-digit number might be handled with five bus conductors and five storage relays (instead of ten) if two energized conductors or actuated relays are simultaneously employed to indicate each number. In other words, the numeral zero would be indicated by bus conductors AB or BA; one-AC or CA: two- AD or DA; three-AE or EA; four-BC or CB; live-BD or DB; six-BE or EB; seven-CD or DC; eight-CE or EC; and nine-DE or ED.

The input for such bus would include a svstem of ten relays each having a pair of secondary circuits. One of these ten relays would correspond to numeral zero and upon closure it would energize the bus conductors A and B. Similarly, the numeral one would energize bus conductors A and C, etc. The output from such a live-conductor bus could be converted to the ten-conductor arrangement by an assembly of live relays connected to the tive bus conductors, each having live poles connected to the live bus conductors. Distribution panels are then utilized to unscramble the twentylive dilerent output possibilities into ten leads corresponding to numerals zero through ninef ln other words, the A relay would have its live poles connected through a distribution panel so that its B pole is connected to the numeral zero lead, the C pole connected to the numeral one lead, etc. Similarly, the B relay would have a distribution panel for converting its A pole to the numeral zero lead, its C pole to the numeral four lead, its B pole to the numeral five lead, etc.

It should be understood that the above examples are 8 merely illustrative, as many variations will occur to those skilled in the art.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. An electrostatic relay comprising elongate upper and lower lixed conductive plates supported in spaced parallel relationship to one another, a series of narrow movable conductive strips extending between the fixed plates, said movable strips being formed of liexible material and being secured at their ends with the free central portion thereof being of a length greater than the straight-line distance between the secured ends, thereby to produce a buckled over-centering eliect in each strip.

2. An electrostatic relay as set forth in claim 1, wherein one of the lixed plates is defined by conductive areas separated by a longitudinal center gap, and an elongate fixed contact mounted in said gap for cooperation with the several movable plates.

3. An electrostatic relay comprising a base panel, an overlying spacer frame, a liexible relay-arm panel overlying said spacer frame, a second spacer frame overelying the relay-arm panel and a top panel overlying the second spacer frame, said panels being formed of insulating material, a lixed plate conductive area on the top surface of the base panel, a fixed plate conductive area on the bottom surface of the top panel, the relay-arm panel being cut to define a movable-plate strip extending between two opposite margins of the panels, movable plate conductive areas on both surfaces of said strip, said strip being secured at its ends between the spacer frames with the free central portion of the strip being of a length greater than the straight-line distance between the secured ends, thereby to introduce a buckle in the strip.

4. An electrostatic relay comprising a lower panel having upward projections at opposite ends and a conductive top surface between said upward projections, an upper panel having downward projections at opposite ends adapted to overlie said upward projections and having a conductive lower surface between said downward projections, and a flexible conductive strip extending between said upper and lower panels, said flexible strip being fixed between said upper and lower projections at both ends of the panel, the intervening portion of the flexible strip extending over the conductive areas of said panels being of a length greater than the straight-line distance between the projections, whereby the interven-y ing portion of said strip is buckled, and said strip having suiiicient resilient iiexibility to develop an overcentering elect in moving from one of said panels to the other panel, whereby said intervening portion tends to remain in one of its two overcentered positions, said overcenterling effect being comparatively weak in comparison with the electrostatic forces developed between said strip and either the upper or lower panel, whereby said strip may be moved electrostatically from one of its overcentered positions to its other overcentered position.

5. An electrostatic relay comprising upper and lower lixed plate-lixed electrodes mounted in spaced relationship from one another, a movable electrode mounted to extend between said lxed electrodes, said movable electrode being formed as a flexible conductive strip with its ends secured so that the intervening center portion is free to move toward and away from either of the lixed electrodes, and a Contact mounted adjacent the center portion of one of said fixed electrodes for cooperation with said movable electrode, said contact being in insulated relationship from the adjacent lixed electrode.

6. An electrostatic relay as set forth in claim 5, wherein said lixed electrodes are formed of resistance material and have circuit connections thereto located adjacent the lixed ends of said movable electrode.

7. An electrostatic relay comprising upper and lower lixed conductive plates supported in spaced parallel re- Alationship to one another and a relay arm extending therebetween, said relay arm being formed of liexible plastic film material having opposed conductive plateforming surfaces, opposite ends of the relay arm being secured in fixed spaced relationship from the fixed plates, and the free central portion of the flexible relay arm being longer than the straight-line distance between its secured ends so as to have a buckled overcentering action.

8. An electrostatic relay comprising upper and lower fixed conductive plates supported in spaced parallel relationship to one another and a relay arm extending therebetween, said relay arm being formed of fiexible plastic film material having opposed conductive plate-forming surfaces, opposite ends of the relay arm being secured in fixed spaced relationship from the fixed plates, and the free central portion of the flexible relay arm being longer than the straight-line distance between its secured ends so as to have a buckled overcentering action, one of the fixed plates being `defined by a conductive area having a center gap, and a contact mounted in said gap for cooperation with the relay arm.

9. An electrostatic relay as set forth in claim 8, wherein the plate with the center gap is connected to the negative terminal of a D.C. power source, the other fixed plate being connected to the positive terminal of said power source, said contact being connected through a normally-closed switch to the positive terminal of said power source, and said plate-forming surfaces of the relay arm being connected through a normally-open switch to the positive terminal of said power source.

10. An electrostatic relay comprising upper and lower fixed conductive plates supported in spaced parallel relationship to one another and a relay arm extending therebetween, said relay arm being formed of flexible plastic lm material having opposed conductive plate-forming surfaces, opposite ends of the relay arm being secured in fixed spaced relationship from the fixed plates, and the free central portion of the fiexible relay arm being longer than the straight-line distance between its secured ends so as to have a buckled overcentering action, at least one of said fixed plates being formed of high-resistance conductive material.

1l. A memory system comprising a group of electrostatic storage relays, each storage relay having first and second fixed plate-like electrodes mounted in spaced relationship from one another, a movable electrode mounted to extend between said fixed electrodes, said movable electrode being formed as a fiexible conductive strip with its ends secured so that the intervening center portion is -free to move toward and away from either of the fixed electrodes, and a Contact mounted adjacent the center f portion of said second fixed electrode for cooperation with said movable electrodes, said contact being in insulated relationship from said second fixed electrode; a group of bus conductors connected to the respective movable electrodes of the several relays for actuating the individual movable electrodes from the first to the second fixed plate, a hold circuit connected to the contact of each relay for holding the movable electrode adjacent the second fixed electrode, and a normally-closed switch connected to break the hold circuit, thereby to permit return of the movable electrode to a position adjacent the first fixed electrode.

l2. A memory system as set `forth in claim l1 further including a multiple-pole address relay, the several poles of which are interconnected in the several bus conductors for the movable electrodes, thereby to open and close the bus conductors to the group of movable electrodes.

13. A memory system as set forth in claim 12 further including a normally-closed clear relay having contact means forming a second hold circuit to the fixed contacts of the several storage relays, the address relay and said clear relay being interconnected whereby closing of the bus conductor circuits effects opening of the clear relay.

14. A memory system as set forth in claim ll wherein the storage relays are divided into two groups and further including at least two multiple-pole address relays, the multiple poles of one relay being connected respectively in the bus conductors leading to the removable electrodes of one group of relays and the multiple poles of the other relay being connected to the respective -bus conductors leading to the removable electrodes of the second group of relays.

References Cited in the le of this patent UNITED STATES PATENTS 749,775 Lacour Ian. 19, 1904 2,201,879 Blattner May 21, 1940 2,243,921 Rust June 3, 1941 2,365,738 Williams Dec. 26, 1944 2,744,245 Low May l, 1956 2,769,968 Schultheis Nov. 6, 1956 2,859,428 Young Nov. 4, 1958 FOREIGN PATENTS 79,668 Sweden Aug. l5, 1929 

